Method and apparatus for converting grain hulls to ash

ABSTRACT

A method for converting dried grain hulls to an essentially carbonless ash material by first removing moisture and volatile gases to form char in an enclosed converter using heat and then burning the char at a controlled rate in an enclosure to remove carbon and form the ash.

I United States Patent l 13,568,610

[72] inventor Dwight Hughes [56] References Cited 30! Elliot St. Apt 21, Woodland, Calif. UNITED STATES PATENTS 95695 1 3,201,329 8/1965 Burt 202/118X [211 P 3,362,887 1/1968 Rodgers 202/105x [221 PM 3 471369 10/1969 Cox m1 110/10x [45] Patented Mar-9,1971

Primary Examiner-Kenneth W. Sprague Attorney- Owen, Wickersham & Erickson 54] METHOD AND APPARATUS FOR CONVERTING GRAIN HULLS T0 ASH 7 Claims, 4 Drawing Figs.

[52] US. Cl. 110/18, ABSTRACT: A method for converting dried grain hulls to an 110/24 essentially carbonless ash material by first removing moisture [51] Int. Cl 123g 7/00 and volatile gases to form char in an enclosed converter using [50] Field of Search 202/105, heat and then burning the char at a controlled rate in an enclo- 106, 218; 0/7, 8, 10, 18, 15, 24 sure to remove carbon and form the ash.

----- E CHAR I L I I I I Il I 14 L (1 1 1 1 Patented March 9,1971 v 356mm INVENTOR, DWIGHT HUGHES? Mi'l'iiiQlD AND APPARATUS TOR QONVERTHNG GRAIN BULLS TO ASH This invention relates to an improved method for reducing organic material such as grain hulls to a carbon free ash material and it also relates to apparatus for carrying out the method.

Organic materials such as certain grain hulls or husks can become valuable products when reduced to a substantially pure ash material free of the carbon moisture and volatile gases contained in the natural material. Rice hulls reduced to ash in the aforesaid manner have proved to be particularly useful as a material for absorbing grease and oil such as in garages and the like. Although ash material has been produced from raw rice hulls for some time, the process used heretofore was relatively crude and ineiiicient and amounted merely to burning the hulls in a pit or an enclosure. Because the raw hulls contain moisture, volatile gases and carbon, the simple burning procedure often produced excessive heat, required a long burning period and sometimes produced an end product of inferior quality.

Another problem which arose in connection with the simple burning process heretofore employed was that of air pollution. in the combustion of the grain hulls directly, the volatile gases created were allowed to escape to the atmosphere and created substantial quantities of acrid smoke and polluted air. Such conditions, particularly in populated areas, became intolerable, and a solution to this problem was necessary to allow the reduction of grain hull ash products to continue.

A general object of the present invention is to provide an improved method for converting organic materials, particularly rice hulls, to ash which overcomes the aforesaid problems and disadvantages.

Another object of the present invention is to provide a method for converting rice hulls to an ash material free from moisture, carbon and volatile gases, which is more efficient, requires less time, is more easily controllable and thus produces a higher yield of pure ash material.

Another object of my invention is to provide a method for reducing grain hulls to a pure ash material that substantially eliminates the air pollution problem by preventing the release of volatile gases to the atmosphere.

Yet another object of the present invention is to provide a burning enclosure for use in carrying out my method that will enable a large quantity of char material to burn and produce ash while the heat produced is controlled and kept relatively low to prevent damage to the structure.

The aforesaid and other objects of my invention are accomplished by a method which broadly includes the steps of first placing the raw material such as rice hulls in a converter unit. The material within the converter unit is heated to drive off moisture and volatile gases, thereby producing a char product. The char product, when sufficiently cooled to facilitate handling, is transferred to a burning enclosure and is distributed therein so that a slow, controlled burning is accom plished. The burning may also be controlled by a series of pipes in the bottom of the enclosure which are perforated to provide streams of upwardly directed air. The burning occurs on an upper layer of material within the enclosure, the ash material thereby gradually building up beneath the burning layer. When the enclosure is filled the upper layer is allowed to burn out and cool so that the end product can be removed.

Other objects, advantages and features of my invention will become apparent from the following detailed description thereof taken with theaccompanying drawings, in which:

1F lGS. 3-3 are a series of schematic views showing the principle steps of my method in which H6. 1 represents a quantity of raw material, PEG. 2. shows a converter apparatus and HG. Ii shows a burning enclosure; and

hit}. a is a view in section of the burning enclosure taken along line 4-4 of FIG. 3.

Referring to the drawing, FlGS. 1-3 illustrate the steps of my method for converting an organic raw material such as rice hulls to an ash substantially free of carbon, moisture and volatile gases. Although my method is particularly adaptable for and will be described in terms of converting rice hulls, it will be apparent that it is also applicable to the conversion of other organic materials. As shown in FIG. l, the raw rice hulls iii are provided in bulk form after the rice kernels have been removed. Generally the moisture content of these hulls is below l214 percent, since this is the moisture level required when the rice is harvested and hulled. The bulls are now fed to a suitable converter or rotary kiln 112. Such devices which are commercially available in various sizes generally comprise a rotary drum 14 into one end of which the raw material such as rice hulls are fed. Preferably, the raw material is continuously fed into the drum as it rotates, and as the material is processed to the char condition, it is continuously removed from the other end of the drum or kiln. As the drum rotates it is continuously heated as by a series of gas heaters 116, and the moisture and volatile gases contained in the rice hulls are driven off. The volatile gases produced from rice hulls are not released to the atmosphere but are collected and also burned within the converter to help heat the drum and increase the efficiency of the converter. The use of the volatile gases also prevents air pollution. Within the converter the rice hulls are heated to a temperature in the range of 1,000 to 2,000 F. depending on such factors as the moisture content and feed rate through the drum. The product that exits from the drum is called char and is designated by the numeral 13. l have found that a satisfactory char product from rice hulls can be produced at a temperature of around l,400 1F., and when it is removed from the converter, it is free from moisture and gases but has a large content of carbon that must be removed.

As shown in FIG. 3, the next step of my method is to burn the char material 18 until the carbon is consumed and only the ash product remains. To accomplish this step, i provide an elongated burning enclosure 20 which is much like a simple house or shed. This enclosure, as shown in FIGS. 3 and 4, has sidewalls 22 which are made of some heat resistant material such as bricks or heavy sheet metal such as iron sheeting. Extending upwardly from the sidewalls is a pitched roof 2 6, also made of a heat resistant sheet material such as asbestos or corrugated transite. Along the inside of the ridge of the roof is a distribution pipe 26 which is provided with a series of spaced apart openings 28. The char material from the converter is blown into the distribution pipe at one end and falls by gravity through the openings in the pipe to the interior of the enclosure below. Thus, the char material is distributed the full length of the enclosure. When the char is initially brought into the enclosure a substantial layer 3% is preferably formed before it is ignited, and commences to burn steadily as a large body of coals without an appreciable amount of flame. As this burning takes place, a layer of ash 32 is produced and builds up as the new char i8 is continuously added. in some instances, may carry out the burning step by merely filling the enclosure to capacity before lighting the char, and in this procedure no char is added during the burning period. The gases produced by this burning, principally carbon dioxide, rise upwardly and exit from the enclosure through an opening 34 along the roof ridge or at any other convenient opening. When the capacity of the burning enclosure is reached, the top body of char is allowed to burn out and the ash remaining is removed for packaging.

Within the enclosure I may provide a series of parallel, spaced apart pipes 36 extending either longitudinally or laterally and horizontally near its bottom through which air may be blown or sucked by a fan 3%. The latter is connected to a manifold pipe 4B0 that interconnects the ends of the parallel pipes 36. Each of the pipes 36 is provided with a series of small, spaced apart openings 42 along its upper side, and during the burning step within the enclosure a relatively small flow of air through the pipes 36 is forced upwardly through the The ash produced by the conversion of rice hulls using the aforesaid method is essentially silica and has alight gray, white or pink color as contrasted with the black color of the char. This rice hull ash is unusually effective in absorbing grease, oil and other hydrocarbons, and thus is widely used where such materials must be cleaned up or controlled.

From the foregoing it should be apparent that the present invention provides an improved method for converting grain hulls in a manner that is not only efficient but is adaptable to high production rates.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. A method for producing a grease absorbing material comprising the steps of:

providing a quantity of natural grain husks or hulls removed from their grain kernels;

applying heat to said husks or hulls to remove moisture and volatile gases to form a char product;

directing air upwardly through the char product while it is confined within an enclosure to control its burning rate; and

burning said char product within the enclosure to remove carbon and thereby leave a pure ash material.

2. The method as described in claim 1 wherein said natural grain husks or hulls are rice hulls having a moisture content of around 14 percent or less.

3. The method as described in claim 2 wherein said hulls are heated to around 1,400 F. in a converter unit to form said char product;

4. The method as described in claim 2 wherein said char product is burned slowly within an enclosure in a substantially uniform layer and wherein said char product is fed evenly to said burning layer over its entire area.

5. An enclosure for burning a char product at a substantially even rate to produce a carbon free ash product comprising an elongated pair of sidewalls and end walls connecting said sidewalls, a pitched roof comprised of a pair of sections diverging upwardly from the upper edges of said sidewalls and connected together along a ridge line, and a distribution pipe on the inside of said roof sections along said ridge line having an opening at one end for receiving char product and a series of spaced apart downwardly directed openings along its length for distributing the char product evenly over the area of the enclosure below.

6. The enclosure as described in claim 5 wherein said sidewalls are made of sheet iron and said roof sections are of an asbestos material.

7. The enclosure as described in claim 5 including a plurality of horizontal, spaced apart pipes supported within said enclosure near its bottom, each said pipe having a series of openings spaced apart along its length; conduit means connecting the ends of said pipes; and fan means connected to said conduit means for forcing air through said pipes. 

2. The method as described in claim 1 wherein said natural grain husks or hulls are rice hulls having a moisture content of around 14 percent or less.
 3. The method as described in claim 2 wherein said hulls are heated to around 1,400* F. in a converter unit to form said char product.
 4. The method as described in claim 2 wherein said char product is burned slowly within an enclosure in a substantially uniform layer and wherein said char product is fed evenly to said burning layer over its entire area.
 5. An enclosure for burning a char product at a substantially even rate to produce a carbon free ash product comprising an elongated pair of sidewalls and end walls connecting said sidewalls, a pitched roof comprised of a pair of sections diverging upwardly from the upper edges of said sidewalls and connected together along a ridge line, and a distribution pipe on the inside of said roof sections along said ridge line having an opening at one end for receiving char product and a series of spaced apart downwardly directed openings along its length for distributing the chAr product evenly over the area of the enclosure below.
 6. The enclosure as described in claim 5 wherein said sidewalls are made of sheet iron and said roof sections are of an asbestos material.
 7. The enclosure as described in claim 5 including a plurality of horizontal, spaced apart pipes supported within said enclosure near its bottom, each said pipe having a series of openings spaced apart along its length; conduit means connecting the ends of said pipes; and fan means connected to said conduit means for forcing air through said pipes. 